How to Make a Mobile PowerBank

About: Hello Guys, I am techgenie, an Electronics hobbyists, tech tinker and developer. I dedicate my free time in designing and making various creative and innovative projects, RC toys, Incredible Gadgets, Awesome...
More About Techgenie »

Powerbanks are an essential products for our Energy consuming gadgets..It is very difficult to maintain the battery charge throughout the day while using your phone to even half its potential. So, it is important to keep a backup supply always.

In this Instructable, i decided to use my old Laptop battery and make a mobile powerbank from the salvaged cells. A Laptop battery needs replacement every few years but all the Li-ion cells inside it are never damaged. They can be extracted and used for various other purposes.

Note: This PowerBank is only capable of charging Android devices. To charge an ios device it needs a special value of voltage (D+ = 2.76v & D- = 2.06v for 1A current draw and d+ = 2.0v & D- = 2.0v for 500mA current draw) at the data pins that can be easily made using a voltage divider circuit with few resistors. But since i needed it for android devices, so didn't worry much about providing voltage at data pins.

From Home & Local Store: Cardboard, Double Sided Tape and Connecting Wires.

Step 2: Watch the Video

A video is a wonderful tool that provides deep insight to the procedure and makes it easy to follow. However, also visit next steps for additional details and images.

Step 3: Prepare Li-Ion Batteries

In case you bought new Li-Ion cells, you can skip this step.

If you are also using an old Laptop battery like me, then you can proceed. The laptop batteries are made up of multiple Li-ion cells connected together in certain combinations. When the battery stops charging or becomes faulty, it has mostly been seen that only few cells get damaged, whereas all other cells work well. We will use those cells to make a powerbank at home.

Carefully open the laptop battery without damaging the cells inside.

Using wire stripper, cut the solder tabs connecting the cells.

Separate each cells and clean them with a damp cloth to remove the adhesive.

Using a multimeter, check the voltage of each individual cells.

Discard the cells with voltage less than 2.5v as they might be damaged and will be difficult to revive.

I got four perfectly working batteries out of six.

Step 4: Connect the Cells

Clean the cell terminals properly and if required, you can also sand them gently using sandpaper.

Place all the cells adjacent to eachother.

Apply some solder over the terminals. Note: Make sure to be quick and prevent cells from getting hot.

Take solder tabs and apply solder to both the edges.

Place the solder tab over the cells and connect it to the cell terminal using soldering iron.

Connect all the cells in parallel using the solder Tabs.

Each cell is 3.7v 2200 mAh, so now we have a 3.7v 8800 mAh battery bank.

Also, connect wires to the battery terminals.

Step 5: Make the Enclosure

Take a sheet of cardboard.

Place the battery over the cardboard and mark the dimensions.

Using the dimensions, make a box to fit the batteries and the electronic circuit.

No, you don't need to control the current. The powerbank should be capable to supply enough current and the device only draws the current it needs.I connected four 2000mAh Li-ion batteries in parallel making a current capacity of 8000mAh or 8Ah.

The design you showed seems good but the batteries cannot be charged with a 5v mobile adapter because the two batteries connected in series have resultant of 7.4v 4000mah current(two such piar makes it 7.4v, 8000mAh), for this you atleast need a 9v 2A power adapter to efficiently charge all the 4 batteries in around 5 hrs. Also, there is no over-discharge protection.